A typical microwave antenna designed for transmitting microwave energy comprises one or more metallic conductors that are electrically connected through a transmission line to a microwave generator. During use, the antenna acts as an impedance transformer between the microwave source and the medium to which the system is transmitting microwave energy. From a circuit perspective, the medium is equivalent to the load where the microwave energy from the microwave generator is ultimately deposited.
The antenna impedance is typically matched to the impedance of the microwave source to maximize the power transfer or minimize reflection of microwave power from the antenna and the medium. For a typical 50-ohm system, at the resonant frequency of the antenna, the antenna impedance presents itself to the transmission line as a pure 50-ohm resistance. At a frequency away from the resonant frequency, the antenna impedance can deviate from the pure resistance and can also have a reactance component: i.e. capacitance or inductance. Thus the system works most efficiently i.e. transmits maximum amount of power at the resonant frequency. During actual use, microwave generators typically generate microwave energy within a well defined frequency range (i.e. operating bandwidth). Therefore, antennas are typically designed such that the resonant frequency of the antenna is around this frequency range. Thus, any variation in the surrounding medium or the antenna itself during use can cause a sufficiently large change in the resonant frequency of the antenna such that the system performance deteriorates or otherwise changes.
Thus, there is a need for an improved design to avoid the problems described above. For example, an improved device and/or method can determine the change in variation in the surrounding medium or the antenna during use and use that information to take additional steps if necessary to improve delivery of microwave energy.